Elective Mutism, (currently classified under "other disorders of childhood") is a poorly understood and difficult to treat disorder. This current work is the largest systematic study of a group of children with this disorder. Our findings suggest that this diagnostic entity may describe a heterogenous group of children, many of whom may be best characterized as having an anxiety disorder (such as social phobia), and may be mediated by a variety of factors. A double-blind controlled trial of fluvoxamine versus placebo is underway, in order to determine whether this intervention may offer effective treatment for this unusual disorder. Preliminary results suggest that it is effective for some. A series of studies of pediatric Seasonal Affective Disorder (SAD) revealed that the disorder is relatively common, with prevalence rates increasing from 1.7% among 6th grade students to 5.5% of high school seniors. Symptomatology varied by gender, with boys exhibiting poor school seniors. Symptomatology varied by gender, with boys exhibiting poor school performance and irritability, while girls with more likely to manifest depressed mood, weight gain, and concentration difficulties. Phototherapy was shown to be effective for this age group in reducing SAD symptoms, in a collaborative study with Mclean Hospital (c. Glod, M. Teicher).